So we have to approach the question by testing assumptions.

The most important assumption is this - does SM keep hypocolors (less than 0) or does it clamp them at 0?

This is a fundamental thing I talked about early on in this thread - that Poser allows us to manipulate colors as arbitrary numbers, even if the intermediate results cannot be "looked at" on a computer monitor.

This is easy to test.

Start with the original texture. Use a brick to subtract white. Then use another brick to add white.

This is (x - k) in the first brick.

Then (x - k) + k in the second brick.

If you do not see x, the original image, then something non-linear happened in the middle. If it is completely white, the intermediate value was clamped.

If SM clamps intermediate results (no less than 0, no more than 1) then you are screwed and cannot make the same things as we can in Poser.

(NOTE: Had to edit - earlier I sad completely black. I meant white.)

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)